Device for measuring voltage across a remote load

Abstract

A device for measuring voltage across a remote load includes a power supply configured to output a first output voltage to the remote load. A switch is selectively movable from a closed position to an open position. A measuring circuit measures a load voltage across the load when the switch is in the open position and determines a voltage difference between the first output voltage and the load voltage. The measuring circuit adjusts the first output voltage to a second output voltage to compensate for the voltage difference. A second A/D converter can also be coupled to the power supply. The second A/D converter measures a voltage across a resistor such that a change in the voltage indicates a change in the load voltage. The power supply is then adjusted to output a second output voltage to compensate for any change in load voltage.

What is claimed is: 
     
       1. A device for measuring voltage across a remote load, comprising:
 a) a power supply coupled to the remote load by a pair of wires, the power supply comprising:
 i) a power output module configured to output a first output voltage to the remote load; 
 ii) a receiver configured to receive voltage information from the remote load; and 
 iii) a first switch unit configured to selectively couple respective first ends of the pair of wires to either the power output module or the receiver; 
 
 b) a measuring circuit coupled to the load and configured to measure a load voltage across the load, the measuring circuit comprising:
 i) a load capacitor connected in parallel with the load wherein the load capacitor supplies the load voltage to the load when the first switch is selected to couple the respective first ends of the pair of wires to the receiver; 
 ii) a first analog to digital (A/D) converter, the first A/D converter configured to measure the load voltage supplied by the load capacitor and packet the measured load voltage into the voltage information; 
 iii) a transmitter in communication with the first A/D converter, the transmitter configured to receive the voltage information from the first A/D converter and transmit the voltage information to the receiver; and 
 iv) a second switch unit configured to selectively couple respective second ends of the pair of wires to either the load or the receiver, 
 wherein when the first switch unit couples the respective first ends of the pair of wires to the power output module, the second switch unit is selected to couple the respective second ends of the pair of wires to the load, and wherein when the first switch unit is selected to couple the respective first ends of the pair of wires to the receiver, the second switch unit is selected to couple the respective second ends of the pair of wires to the transmitter. 
 
 
     
     
       2. The device of  claim 1  wherein the pair of wires is configured to operate as a differential pair. 
     
     
       3. The device of  claim 1  wherein the first A/D converter, the transmitter or the receiver is configured to calculate a voltage difference between the first output voltage and the load voltage packeted within the voltage information. 
     
     
       4. The device of  claim 3  wherein the receiver is further configured to output an adjustment signal to the power supply to adjust the power supply to output a second output voltage to compensate for the voltage difference. 
     
     
       5. The device of  claim 1  wherein the measuring circuit comprises a second A/D converter coupled to the power supply, the second A/D converter configured to measure a voltage across a resistor wherein a change in the voltage indicates a change in the load voltage, the power supply adjusted to output a second output voltage to compensate for the change in load voltage. 
     
     
       6. A method for measuring voltage across a remote load, comprising:
 a) providing a power supply coupled to the remote load by a pair of wires, the power supply including a power control module configured to output a first output voltage to the remote load, receiver and a first switch unit, and a measuring circuit coupled to the load and configured to measure a load voltage across the load, the measuring circuit including a load capacitor connected in parallel with the load, a first analog to digital (A/D) converter connected to the load, a transmitter in communication with the first A/D converter and a second switch unit; 
 b) toggling the first switch unit to couple respective first ends of the pair of wires to the power control module and toggling the second switch unit to couple respective second ends of the pair of wires to the remote load whereby the power supply module supplies the first output voltage to the remote load; 
 c) toggling the first switch unit to couple the respective first ends of the pair of wires to the receiver whereby the second switch unit toggles to couple the respective second ends of the pair of wires to the transmitter; 
 d) allowing the load capacitor to provide the load voltage to the remote load; 
 e) configuring the first A/D converter to measure the load voltage being supplied to the remote load by the load capacitor; 
 f) packeting the measured load voltage into a voltage information packet; 
 g) communicating the voltage information packet to the transmitter; and 
 h) transmitting the voltage information packet to the receiver. 
 
     
     
       7. The method of  claim 6 , wherein the first A/D converter, the transmitter or the receiver is configured to calculate a voltage difference between the first output voltage and the load voltage packeted within the voltage information packet, the method further comprising:
 i) configuring the receiver to output an adjustment signal to the power output module to adjust the power output module to output a second output voltage to compensate for the voltage difference. 
 
     
     
       8. The method of  claim 6 , wherein the measuring circuit further comprises a second A/D converter and a sense resistor coupled to the power supply, the method further comprising:
 i) configuring the second A/D converter to measure a voltage across the sense resistor wherein the voltage indicates a change in the load voltage; and 
 j) adjusting the power output module to output a second output voltage to compensate for the change in load voltage.